Filter devices for the above uses are known in a large variety of types. For enlarging the volume of the filter medium having the gas or the fluid passing there-through for cleaning, a known approach has been to arrange the filter medium in zig-zag pleats. Thus, in a large number of known filter devices, the filter element comprising the filter medium has a pleated configuration which is exposed to the flow to be cleaned. In most cases, the filter elements are enclosed by a filter element holding frame for stabilization.
Filter devices of the above type are known, e.g., from U.S. Pat. No. 3,246,457, GB-PS 1 570 385 and EP-A-0 450 299. A common disadvantage of these known filter devices resides in that the exchangeable part of the filter device encloses the filter element and the holding frame of the filter element. However, these two components of known filter devices consist of different materials, thus complicating any environmentally friendly disposal of the disposable parts of known filter devices. Further, the quantity of waste or disposable material is considerable because the stabilization of the pleated structure of the filter medium of the filter element necessitates relatively large quantities of material which; when exchanging the filter medium, have to be exchanged as well and thus have to be disposed of.
It to an object of the invention to provide a filter device for the filtration of gases and/or fluids, and particularly a filter device for the filtration of air streaming into the passenger cabin of a motor vehicle, wherein the quantity of material which is not used for the cleaning of games and/or fluids, but which must be disposed nonetheless when replacing a spent filter medium, is as small as possible.
For solving the above object, the invention proposes a filter device of the above type comprising the following features:
A filter element including a filter medium pleated in zig-zag manner and being provided, on its two longitudinal sides extending in the pleating direction, with stabilizing strips for stabilizing the zig-zag-shaped pleated configuration of the filter medium, with said stabilizing strips being directly bonded to the longitudinal edges of the filter medium, PA1 a sealing medium provided on the outer sides of the two stabilizing strips which are facing away from the filter medium, and PA1 a filter element holding frame having longitudinal and transverse portions and being adapted for insertion of the filter element thereinto and for removal of the filter element therefrom, PA1 wherein, when the filter element in inserted in the filter element holding frame, the sealing material of the stabilizing strips is in abutment with the inner sides of said longitudinal frame portions of the filter element holding frame and end portions of the filter medium in the pleating direction are engaged with receiving means provided on said transverse portions of the filter element holding frame.
In the filter means of the invention, the stabilization of the pleated configuration of the filter medium is effected--irrespective of a certain inherent stability of shape of the filter medium in its pleated state only by two stabilizing strips. These stabilizing strips are bonded to the longitudinal edges of the filter medium which ends extend in the pleating direction. The thickness of said stabilizing strips, while being dependent an the material selected for the stabilizing strips, need only be selected in such a manner that the filter medium is given a consistent or regular mechanically stable pleated configuration. Such stabilizing strips or similar suitable measures are not provided on the and portions of the filter medium in the pleating direction. The width of the stabilizing strips along the longitudinal edges of the filter medium corresponds to the height of the pleated structure.
Handling of the filter element of the filter device of the invention in easy and convenient. In order to replace a filter element with its spent filter medium by a now one, the old filter element is taken out of the filter element holding frame and a new filter element in inserted into the holding frame. When the filter element is in its final position in the holding frame, the sealing medium of the two stabilizing strips are in abutment with the inner sides of the longitudinal frame portions of the holding frame. When using the filter device, gases and fluids are prevented by this sealing medium from passing through the space between the filter element and the filter element holding frame without being filtered. At the end portions of the filter medium in the pleating direction, the occurrence of any open air gap extending in the plane of the cross section of the filter element holding frame is precluded by insertion of the end portions into receiving means formed on the transverse portions of the frame. The end portions are inserted into the receiving means at the same time the filter element is inserted into the frame. Preferably, the receiving means are provided as gap-like recesses having their openings directed against the flow direction. These recesses accommodate the full end portions of the filter medium and are arranged in the flow direction. This construction offers the advantage that, on the one hand, insertion of the filter element into the filter element holding frame is simplified and, on the other hand, during use of the filter device, the gas or fluid to be cleaned presses the end portions of the filter medium into the receiving means, so that the filter medium end portions are reliably protected from slipping out of the receiving means during use of the filter device.
In the filter device of the invention, the filter element, i.e. the filter medium with the two stabilizing strips bonded thereto, is the only component which has to be exchanged at the end of the life span of the filter medium. The filter element holding frame, which in preferably placed into a holding means for the filter device, e.g., into the air intake opening of an air condition system, and particularly in a manner allowing exchange of the frame, can be reused. Thus, the quantity of waste material to be disposed in minimized because a very small quantity of material is required for producing the stabilizing strip and the sealing medium.
Preferably, the filter medium, the sealing medium, the strips of stabilizing material and the adhesive agent for connecting the filter medium and the sealing medium to the stabilizing strip will comprise the same plastic material; this plastic material is preferably polypropylene. Thus, disposal and potential reuse of the filter element material is less complicated than with prior art devices since the filter element of the invention is not made from materials which are different from each other. In this regard, the filter device of the invention is environmentally friendly.
In an advantageous embodiment of the invention, it is provided that the filter element holding frame has inclined or at least partially inclined frame portions for facilitating insertion of the filter element. By a filter element holding frame of this form, conically tapering in the direction of insertion of the filter element, handling of the entire device is made still easier.
In an advantageous embodiment of the invention, the receiving means are provided as recessed inserting spaces being delimited, on the one hand, by the frame cross sections of the filter element holding frame and, on the other hand, by flaps or tongues arranged on these cross sections. Said flaps are arranged on the cross sections of the frame and/or on the longitudinal portions of the frame in the region of the ends facing the cross sections of the frame. The two flaps are oriented at a slight inclination toward each other or comprise portions extending at an inclination toward each other so that the space between a flap and the cross section of the frame becomes larger in the upward direction. The flaps can be integrally connected to the filter frame; it will suffice if the flaps extend only over part of the length of the cross sections of the frame, while being arranged, e.g., at a central position with respect to the longitudinal axis of the filter element holding frame. Preferably, the flaps, arranged within the filter element holding frame, engage from below the end portions of the zig-zag shaped filter medium, or at least partially do so. However, the flaps preferably extend across the full cross section of the filter end portions on the downstream or lower edge to prevent passage of air or fluid. The flaps can taper from the upward or upstream edge to the lower or downstream edge to facilitate insertion. Thus, the flaps support the filter medium on the ends of the filter medium in the pleating direction, which contributes to the stabilization of the zig-zag configuration of the filter element.
Preferably, the end portions of the filter element are adapted to be pressed into the receiving means; the distance between the cross section of the frame and the flap is--at least in certain areas (e.g., the downstream edge)--less than the thickness of the filter medium so that the end portions of the filter medium inserted in the receiving means are (slightly) compressed.
Preferably, the sealing medium comprises a material which also fulfills a filtering function. The material of the sealing medium advantageously corresponds to that of the filter medium so that the gases and fluids entering the space between the stabilizing strips of the filter element and the longitudinal frame portions of the filter element holding frame are filtered as well. The sealing medium is suitably a one- or multi-layered non-woven filter which can be used also as a material for the filter medium while being supported by a reticular support structure. Particularly, the sealing medium is provided as a narrow strip whose width in smaller than that of the stabilizing strip to which it is bonded, and which extends over the entire length of the stabilizing strip preferably on the downstream or lower edge. Thus, the sealing medium does not cover the entire outer side of a stabilizing strip, which contributes to economical use of material. Further, insertion of the filter element into the filter element holding frame in facilitated.